WASHINGTON (AP) _ The government's auto safety agency told Chrysler Corp. Friday it was very troubled the automaker was telling minivan owners there was no safety problem with the rear-door latches the company has agreed to replace.

The National Highway Traffic Safety Administration informed Chrysler in a letter it would carefully monitor repairs. The agency also said it would work with Chrysler to revise what employees of their hot line are telling customers to make sure motorists understand there is a safety concern and they should bring their minivans in for repair.

In the spring, Chrysler told the agency it would repair or replace the latches in some 4 million minivans sold from 1984 to 1994 because of fears of ejections from rear liftgates popping open in crashes.

``NHTSA at no time found the latches to be safe,'' Michael Brownlee, the agency's associate administrator of safety assurance, wrote in a letter to Chrysler. It was the second such letter this week and the clearest sign to date of the agency's frustration with Chrysler.

At least 35 people have died in accidents in which the liftgates opened in the Town and Country, Dodge Caravan and Plymouth Voyager minivans, according to public files.

NHTSA was investigating but had made no finding of a defect _ which could lead to a formal recall _ when Chrysler offered in March to repair the latches free.

Later that month, Chrysler took out a newspaper ad telling customers the automaker was ``convinced there is no safety defect in these minivans' liftgate latches, and the National Highway Traffic Safety Administration has not found otherwise.''

NHTSA has been keeping its investigation open until it was satisfied the repair program was well on track. The agency still has the authority to recall the minivans.

Chrysler officials in Highland Park, Mich., did not return phone messages seeking comment.